In recent years, a technique for growing an edible plant or an ornamental plant, irrespective of a season, has been developed. A light source using artificial light is one of such techniques. An absorption spectrum of a photosynthetic pigment related to photosynthesis of a plant is mainly in a blue color region and a red color region, and light in such regions is considered important for growing a plant. Accordingly, a light source that generates light in the blue color region and the red color region is widely known as a light source for growing a plant.
As a light source for growing a plant, a light-emitting diode (hereinafter referred to as “LED”) that can be adjusted in wavelength freely attracts attention. For example, Patent Literature 1 discloses an LED light source for growing a plant, which LED light source uses an LED that generates both (i) light having a wavelength in a range of 400 nm to 480 nm (blue color) and (ii) light having a wavelength in a range of 650 nm to 700 nm (red color). Moreover, Patent Literature 2 discloses a lighting device for growing a plant, which lighting device supplies light necessary for a plant to grow in such a manner that (i) a fluorescent material for emitting blue light is excited by use of an ultraviolet LED and (ii) a fluorescent material for emitting red light is excited by use of an ultraviolet LED.